Reflective exposure mask, and method for producing and using the same

ABSTRACT

When producing an exposure mask including a stack of reflective layers for reflecting extreme ultraviolet light, an absorber film for covering a light reflection plane of the stack of reflective layers with a predetermined pattern, and a buffer film interposed therebetween, the swing effect and the bulk effect that occur on a transferred portion of the predetermined pattern are specified in accordance with characteristic values of forming materials of the absorber film and the buffer film and optical conditions when exposing, and a forming film thickness of the absorber film is decided in consideration of the specified swing effect and the specified bulk effect so that the line width variation of the pattern and/or pattern shift of the pattern are at their minimum values. As a result, even for an exposure mask capable of dealing with extreme ultraviolet light, the line width variation and pattern shift after a wafer is exposed are minimized, and therefore it is possible to realize miniaturization of a transferred image appropriately.

TECHNICAL FIELD

The present invention relates to a method for producing an exposure maskused in a lithography process for forming a circuit pattern of asemiconductor device and to an exposure mask itself. In particular, thepresent invention relates to a method for producing an exposure mask andan exposure mask for so-called extreme ultraviolet light and, moreparticularly, to a method for producing a semiconductor device using theexposure mask.

BACKGROUND ART

In recent years, as semiconductor devices are miniaturized, there areneeds for miniaturizing a pattern width, a pattern pitch (line width),and so forth, of a circuit pattern formed on a wafer, a resist patternfor forming a circuit pattern, and so forth. These needs can besatisfied by using ultraviolet light having a shorter wavelength toexpose the resist pattern. As semiconductor devices are miniaturized,ultraviolet light having short wavelengths is used to expose wafers. Fora semiconductor device produced corresponding to a design rule of 350nm, ultraviolet light having a wavelength of 365 nm is used; forsemiconductor devices produced corresponding to design rules of 250 nmand 180 nm, ultraviolet light having a wavelength of 248 nm is used; andfor semiconductor devices produced corresponding to design rules of 130nm and 100 nm, ultraviolet light having a wavelength of 193 nm is used.Currently, ultraviolet light having even a wavelength of 157 nm is used.

It is known that resolutions corresponding to these wavelengths areexpressed by Rayleigh's formula, w=k1×(λ/NA), where w represents aminimum width of a pattern that is to be resolved, NA represents anumerical aperture of a lens of a projection optical system; λrepresents a wavelength of exposure light; k1 represents a processconstant that depends on the performance of the resist pattern, the useof resolution enhancement technology, and so forth. It is known thatwhen the optimum resist pattern and super high resolution technology areused a process constant of k1=around 0.35 can be selected. In the superhigh resolution technology, ±first order diffraction light that passesthrough a mask and is diffracted by a light insulating pattern on themask is selectively used so as to obtain a pattern smaller than awavelength. Theoretically, a much smaller pattern can be obtained using±n-th order diffraction light (where n≧2). However, the intensity of thediffraction light remarkably decreases. In addition, the pattern isrestricted by the pupil of the projection optical system. Thus, it isnot practical to use ±n-th order diffraction light (where n≧2).

According to the Rayleigh's formula, it is found that when ultravioletlight having a wavelength of 157 nm is used and a lens having NA=0.9 isused, the minimum pattern width is 61 nm. In other words, to obtain apattern width smaller than 61 nm, it is necessary to use ultravioletlight having a shorter wavelength than 157 nm.

Thus, recently, the use of ultraviolet light having a wavelength of 13.5nm, referred to as extreme ultraviolet light, has been considered foruse as ultraviolet light having a shorter wavelength than 157=n.However, there are materials such as calcium fluoride (CaF₂) and silicondioxide (SiO₂) that have light transmissivities for ultraviolet lighthaving a wavelength of up to 157 nm. Thus, a mask and an optical systemthat are capable of transmitting these ultraviolet lights can beproduced. However, there are no materials that are capable oftransmitting extreme ultraviolet light having a wavelength of 13.5 nmwith a desired thickness. Thus, when extreme ultraviolet light having awavelength of 13.5 nm is used, it is necessary to structure a mask andan optical system as a reflective type mask and a reflection typeoptical system that reflects light rather than a light transparent maskand a light transmission type optical system, respectively.

When a light reflective type mask and a light reflection type opticalsystem are used, light reflected on a mask surface has to be guided to aprojection optical system without interference with light that entersthe mask Thus, light that enters the mask should inevitably have anincident angle of φ against the normal line of the mask surface. Thisangle depends on the numerical aperture NA of the lens of the projectionoptical system, magnification m of the mask, and the size σ of thelighting source. More specifically, when a mask having a reductionfactor of, for example, 5× is used on a wafer, in an exposure apparatushaving NA=0.3 and σ=0.8, light enters the mask at a solid angle of3.44±2.75 degrees. When a mask having a reduction factor of 4× is usedon a wafer, in an exposure apparatus having NA=0.25 and σ=0.7, lightenters the mask at a solid angle of 3.58±2.51 degrees.

As a reflective type mask that deals with inclined incident light, amask includes a stack of reflective layers, hereinafter referred to asmask blanks, that reflect extreme ultraviolet light, an absorber filmthat covers the mask blanks with a predetermined pattern and absorbsextreme ultraviolet light, and a buffer film interposed between the maskblanks and the absorber film The mask blanks are constituted by astructure composed of molybdenum (Mo) layers and silicon (Si) layersthat are alternately laminated. Generally, the mask blanks are composedof a total of 40 layers of molybdenum layers and silicon layers. Whenthe absorber film that absorbs extreme ultraviolet light is coated in apredetermined pattern on the mask blanks, incident light is selectivelyreflected corresponding to a circuit pattern, a resist pattern, and soforth that are to be formed. The buffer film is disposed as an etchingstopper that prevents the stack of reflective layers from being etchedor to avoid being damaged when defects have been removed from the formedabsorber film.

When the foregoing reflective type mask is produced, it is necessary toproperly decide the film thickness of the absorber film. Conventionally,the film thickness of the absorber film is decided in accordance with anoptical density (hereinafter referred to as “OD”) of the absorber film,for example, OD=3. The film thickness of the absorber film thatsatisfies OD=3 is a film thickness that causes the intensity of incidentlight to be attenuated to 1/1000. As described in, for example,“Proceedings of SPIE vol. 4343 (2001) pp 409-414 “TaN EUVL MaskFabrication and Characterization”, the value of the OD depends on thereflectance of the surface of the absorber film. The film thickness isdecided in accordance with the OD obtained from the reflectance of thesurface of the absorber film because a transparent mask that is notcapable of dealing with extreme ultraviolet light employs that method.

However, when a reflective type mask dealing with extreme ultravioletlight is used, if the film thickness of the absorber film is decided inaccordance with the OD obtained from the reflectance of the surface ofthe absorber film, the line width variation and the pattern shift to betransferred to a wafer may become large. In the case of the reflectivetype mask, although the absorber film and the buffer film are formed onthe mask blanks that reflect extreme ultraviolet light, the swing effectand the bulk effect may occur on a transferred image on a wafer due tomultiple reflections in the absorber film and the buffer film.

More specifically, when the thicknesses of the absorber film and thebuffer film are approximately 100 nm and 30 nm, respectively, thesethicknesses are larger than a wavelength of 13.5 nm of extremeultraviolet light, the standing wave effect occurs between extremeultraviolet light and light reflected by the mask blanks. This standingwave periodically varies the line width and position of the pattern tobe transferred to the wafer. In other words, the swing effect, in whichthe line width and pattern position periodically swing, and the bulkeffect, in which they do not periodically vary, occur.

Thus, when the film thickness of the absorber film is decided inaccordance with the OD obtained from the reflectance of the surface ofthe absorber film, the film thickness of the absorber film may bedecreased so as to reduce the influence of the light insulating effectof the absorber film (for example, OD=2). However, the foregoing swingeffect and bulk effect may cause the line width variation and patternshift to become too large. As a result, the needs for miniaturizing thepattern width, pattern pitch, and so forth of a transferred image wouldnot be properly satisfied.

Therefore, an object of the present invention is to provide an exposuremask, a method for producing an exposure mask, and a method forproducing a semiconductor device, the exposure mask being a reflectivetype mask being capable of dealing with extreme ultraviolet light, thefilm thickness of an absorber film being decided so that the line widthvariation and pattern shift of a pattern exposed on a wafer are at theirminimums and so that the exposure mask contributes to the improvement ofthe performance of a semiconductor device (appropriate address forminiaturization).

DISCLOSURE OF THE INVENTION

To accomplish the foregoing objects, the present invention provides amethod for producing an exposure mask. In other words, the presentinvention provides a method for producing an exposure mask, which isused for exposing an exposure object with the extreme ultraviolet lightin a process for producing a semiconductor device, having mask blanksfor reflecting extreme ultraviolet light; an absorber film functioningto absorb the extreme ultraviolet light for covering a light reflectionplane side of the mask blanks with a predetermined pattern; and a bufferfilm interposed between the mask blanks and the absorber film. Thismethod includes the steps of specifying the swing effect and bulkeffect, which occur on a transferred image on the exposure object due tomultiple reflections within the absorber film and the buffer film to atleast one fluctuation of a line width and pattern shift in a transferredportion of the predetermined pattern, in accordance with characteristicvalues of forming materials of the absorber film and the buffer film andoptical conditions when exposing, upon deciding the forming filmthickness of the absorber film; and deciding an optical density that isa deciding condition of a forming film thickness of the absorber film inconsideration of the specified swing effect and the specified bulkeffect so that the line width variation of the pattern and/or thepattern shift are at their minimum.

According to the forgoing method for producing the exposure mask, sincethe optical density as a deciding condition of the forming filmthickness of the absorber film is decided in consideration of the swingeffect and the bulk effect that occur on the transferred image on theexposure object, when the forming film thickness of the absorber film isdecided in accordance with the optical density, unlike the case in whichthe optical density is only decided in accordance with the reflectanceof the surface of the absorber film, even if the swing effect and thebulk effect occur on the transferred image on the exposure object, theforming film thickness of the absorber film can be decided so that theline width variation of the transferred image is at its minimum.

In addition, the present invention provides a method for producing anexposure mask the method including the steps of specifying a swingeffect and bulk effect, which occur on a transferred image on anexposure object due to multiple reflections within an absorber film anda buffer film to at least one fluctuation of a line width and patternshift of a predetermined pattern, in accordance with characteristicvalues of the forming materials of the absorber film and the buffer filmand optical conditions when exposing, upon deciding the forming filmthickness of the absorber film; and deciding the forming film thicknessof the absorber film in consideration of the specified swing effect, thespecified bulk effect, and forming accuracy of the absorber film so thatthe line width variation of the pattern and/or the pattern shift are attheir minimum.

According to the above method for producing an exposure mask when theforming film thickness of the absorber film is decided, since the swingeffect and the bulk effect that occur on the transferred image of theexposure object and the film forming accuracy of the absorber film areconsidered, unlike the case in which the forming film thickness of theabsorber film is decided in accordance with the optical densityspecified from only the reflectance of the surface of the absorber film,even if the swing effect and bulk effect occur on the transferred imageof the exposure object or even if the forming film thickness fluctuatesdue to influence of the film forming accuracy of the absorber film, theforming film thickness of the absorber film can be decided so that theline width variation of the transferred image is at its minimum.

In addition, to accomplish the foregoing object, the present inventionprovides an exposure mask. In other words, the present inventionprovides an exposure mask, which is used for exposing an exposure objectin a producing process for a semiconductor device, including mask blanksfor reflecting exposure light; an absorber film functioning to absorbthe exposure light for covering a light reflection plane side of themask blanks with a predetermined pattern; and a buffer film interposedbetween the mask blanks and the absorber film, wherein a swing effectand a bulk effect, which occur on a transferred image on the exposureobject due to multiple reflections within the absorber film and thebuffer film to at least one of fluctuation of a line width and patternshift of a predetermined pattern are specified in accordance withcharacteristic values of forming materials of the absorber film and thebuffer film and optical conditions when exposing, and wherein an opticaldensity that is a deciding condition of a forming film thickness of theabsorber film is decided in consideration of the specified swing effectand the specified bulk effect so that the line width variation of thepattern and/or the pattern shift are at their minimum.

According to the above exposure mask, since the swing effect and thebulk effect that occur on the transferred image on the exposure objectare considered in deciding the optical density that is a decidingcondition of forming a film thickness of the absorber film, when theforming film thickness of the absorber film is decided in accordancewith the optical density, unlike the case in which the forming filmthickness of the absorber film is decided in accordance with the opticaldensity specified from only the reflectance of the surface of theabsorber film, even if the swing effect and bulk effect occur on thetransferred image of the exposure object, the forming film thickness ofthe absorber film can be decided so that the line width variation of thetransferred image is at its minimum.

In addition, the exposure mask of the present invention is used forexposing an exposure object in a producing process for a semiconductordevice and includes mask blanks for reflecting exposure light; anabsorber film functioning to absorb the exposure light for covering alight reflection plane side of the mask blanks with a predeterminedpattern; and a buffer film interposed between the mask blanks and theabsorber film, wherein a swing effect and a bulk effect, which occur ona transferred image on the exposure object due to multiple reflectionswithin the absorber film and the buffer film to at least one offluctuation of a line width and pattern shift in a transferred portionof the predetermined pattern are specified in accordance withcharacteristic values of forming materials of the absorber film and thebuffer film and optical conditions when exposing, and wherein a formingfilm thickness of the absorber film is decided in consideration of thespecified swing effect, the specified bulk effect, and the film formingaccuracy of the absorber film so that the line width variation of thepattern and/or the pattern shift are at their minimum.

According to the exposure mask structured above, when the forming filmthickness of the absorber film is decided, since the swing effect andthe bulk effect that occur on the transferred image on the exposureobject and the film forming accuracy of the absorber film are consideredto decide the forming film thickness of the absorber film, unlike thecase in which the forming film thickness of the absorber film is decidedin accordance with the optical density specified from only thereflectance of the surface of the absorber film, even if the swingeffect and bulk effect occur on the transferred image on the exposureobject or even if the forming film thickness fluctuates due to influenceof the film forming accuracy of the absorber film, the forming filmthickness of the absorber film can be decided so that the line widthvariation of the transferred image becomes minimal.

In addition, the present invention provides a method for producing asemiconductor device. In other words, the present invention provides amethod for producing a semiconductor device, including the step ofproviding an exposure mask having mask blanks for reflecting exposurelight; an absorber film functioning to absorb the exposure light forcovering a light reflection plane side of the mask blanks with apredetermined pattern; and a buffer film interposed between the maskblanks and the absorber film; the exposure mask being produced by amethod having the steps of specifying a swing effect and a bulk effect,which occur on an transferred image on the exposure object due tomultiple reflections in the absorber film and the buffer film to atleast one fluctuation of a line width and pattern shift in a transferredportion of the predetermined pattern, in accordance with characteristicvalues of forming materials of the absorber film and the buffer film andoptical conditions for exposing, upon deciding the forming filmthickness of the absorber film; and deciding an optical density that isa deciding condition of a forming film thickness of the absorber film inconsideration of the specified swing effect and the specified bulkeffect so that the line width variation of the pattern and/or thepattern shift are at their minimum; and exposing the exposure objectwith the exposure mask using exposure light having the same wavelengthas the exposure light used by the method for producing the exposuremask.

According to the forgoing method for producing the semiconductor device,at the exposing step for exposing the exposure object, since the opticaldensity as a deciding condition of the forming film thickness of theabsorber film is decided in consideration of the swing effect and thebulk effect that occur on the transferred image on the exposure object,when the forming film thickness of the absorber film is decided inaccordance with the optical density, unlike the case in which theoptical density is decided in accordance with only the reflectance ofthe surface of the absorber film, even if the swing effect and the bulkeffect occur on the transferred image on the exposure object, theforming film thickness of the absorber film can be decided so that theline width variation of the transferred image is at its minimum.

In addition, the present invention provides a method for producing asemiconductor device, including the step of providing an exposure maskhaving mask blanks for reflecting exposure light; an absorber filmfunctioning to absorb the exposure light for covering a light reflectionplane side of the mask blanks with a predetermined pattern; and a bufferfilm interposed between the mask blanks and the absorber film; theexposure mask being produced by a method having the steps of specifyinga swing effect and a bulk effect, which occur on a transferred image onthe exposure object due to multiple reflections in the absorber film andthe buffer film to at least one fluctuation of a line width patternshift in a transferred portion of the predetermined pattern inaccordance with characteristic values of forming materials of theabsorber film and the buffer film and optical conditions when exposing,upon deciding the forming film thickness of the absorber film; anddeciding a forming film thickness of the absorber film in considerationof the specified swing effect, the specified bulk effect, and a formingaccuracy of the absorber film so that the line width variation of thepattern and/or the pattern shift are at their minimum; and exposing theexposure object with the exposure mask using exposure light having thesame wavelength as the exposure light used by the method for producingthe exposure mask.

According to the method for producing the semiconductor device, when theforming film thickness of the absorber film of the exposure mask isdecided, since the swing effect and the bulk effect that occur on thetransferred image of the exposure object and the film forming accuracyof the absorber film are considered, at the exposing step for exposingthe exposure object, unlike the case in which the forming film thicknessof the absorber film is decided in accordance with the optical densityspecified from only the reflectance of the surface of the absorber film,even if the swing effect and bulk effect occur on the transferred imageof the exposure object or even if the forming film thickness fluctuatesdue to an influence of the film forming accuracy of the absorber film,the forming film thickness of the absorber film can be decided so thatthe line width variation of the transferred image is at its minimum.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing an example of an outlined structureof an exposure mask according to the present invention.

FIG. 2 is a flow chart showing an example of a process for deciding afilm thickness of a TaN film of the exposure mask according to thepresent invention.

FIG. 3 is a schematic diagram describing a concrete example of the swingeffect and the bulk effect with plotted values against a line width fora film thickness of a TaN film in the case that a pattern having a widthof 40 nm is formed on a mask (on a wafer: 160 nm on a 4× mask).

FIG. 4 is a schematic diagram describing a concrete example of the swingeffect and the bulk effect with plotted values against a pattern shiftfor a film thickness of a TaN film in the case that a pattern having awidth of 40 nm is formed on a mask (on a wafer: 160 nm on a 4× mask).

FIG. 5 is a schematic diagram describing a concrete example of only theswing effect with plotted values against a line width for a filmthickness of a TaN film in the case that a pattern having a width of 40nm is formed on a mask (on a wafer: 160 nm on a 4× mask).

FIG. 6 is a schematic diagram describing a concrete example of only theswing effect with plotted values against pattern shift for a filmthickness of a TaN film in the case that a pattern having a width of 40nm is formed on a mask (on a wafer: 160 nm on a 4× mask).

FIG. 7 is a schematic diagram describing a concrete example of therelation of an OD and a film thickness of a TaN film.

FIG. 8 is a schematic diagram describing a concrete example of the swingeffect and the bulk effect with plotted values against a line width inthe case that a pattern having a width of 40 nm is formed on a mask (ona wafer: 160 nm on a 4× mask) and that a film thickness of a TaN film isfixed and a film thickness of a Ru film is varied with an OD of around3.

FIG. 9 is a schematic diagram describing a concrete example of the swingeffect and the bulk effect with plotted values against a pattern shiftin the case that a pattern having a width of 40=n is formed on a mask(on a wafer: 160 nm on a 4× mask) and that a film thickness of a TaNfilm is fixed and a film thickness of a Ru film is varied with an OD ofaround 3.

FIG. 10 is a schematic diagram describing a concrete example of theswing effect and the bulk effect with plotted values against a linewidth in the case that a pattern having a width of 40 nm is formed on amask (on a wafer: 160 nm on a 4× mask) and that film thicknesses of aTaN film and a Ru film are varied with an OD of around 3.

FIG. 11 is a schematic diagram describing a concrete example of theswing effect and the bulk effect with plotted values against a patternshift in the case that a pattern having a width of 40 nm is formed on amask (on a wafer: 160 nm on a 4× mask) and that film thicknesses of aTaN film and a Ru film are varied with an OD of around 3.

FIG. 12 is a schematic diagram describing a concrete example of theswing effect and the bulk effect with plotted values against a linewidth in the case that a pattern having a width of 30 nm is formed on amask (on a wafer: 120 nm on a 4× mask) and a film thicknesses of a TaNfilm and a Ru film are varied at an incident angle of 4.84 degrees.

FIG. 13 is a schematic diagram describing a concrete example of theswing effect and the bulk effect with plotted values against a patternshift in the case that a pattern having a width of 30 nm is formed on amask (on a wafer: 120 nm on a 4× mask) and a film thicknesses of a TaNfilm and a Ru film are varied at an incident angle of 4.84 degrees.

FIG. 14 is a schematic diagram describing a concrete example of theswing effect and the bulk effect with plotted values against a linewidth in the case that a pattern having a width of 30 nm is formed on amask (on a wafer: 120 nm on a 4× mask) and a film thicknesses of a TaNfilm and a Ru film are varied at an incident angle of 7.27 degrees.

FIG. 15 is a schematic diagram describing a concrete example of theswing effect and the bulk effect with plotted values against a patternshift in the case that a pattern having a width of 30 nm is formed on amask (on a wafer: 120 nm on a 4× mask) and that film thicknesses of aTaN film and a Ru film are varied at an incident angle of 7.27 degrees.

FIG. 16 is a flow chart showing an example of a process of a method forproducing a semiconductor device including a step for using an exposuremask according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, with reference to the accompanying drawings, a method forproducing an exposure mask, an exposure mask, and a method for producinga semiconductor device according to the present invention will bedescribed. It should be noted that the present invention is not limitedto the following embodiments.

First of all, a structure of an exposure mask according to the presentinvention will be described. FIG. 1 is a perspective view showing anexample of an outlined structure of the exposure mask according to thepresent invention. As shown in the figure, an exposure mask 10 iscomposed of mask blanks 12 of which a total of 40 layers of Mo layersand Si layers are alternately laminated on, for example, a silicondioxide (SiO₂) glass 11; a buffer film 13 made of ruthenium (Ru)(hereinafter referred to as “Ru film”); and an absorber film 14 made oftantalum nitride (TaN) as a material of absorbing extreme ultravioletlight (hereinafter referred to as “TaN film”).

The characteristic values of the forming materials of those filmsconstituting the exposure mask 10 are as follows. The film thicknessesof the Mo layer and the Si layer constituting the mask blanks 12 are2.789 nm and 4.184 nm, respectively. The film thickness of the Ru film13 is 30 nm satisfy the function as a buffer film. The refractiveindexes of the forming materials are as follows:

SiO₂=0.9781727−0.0107731i,

Mo=0.9210839−0.00643543i,

Si=0.999319676−0.00182645i,

Ru=0.887487−0.0174721i,

TaN=0.9413643−0.0315738i

where i is an imaginary unit.

An optical condition when exposure is performed with the exposure mask10 is as follows. In other words, an exposure wavelength is 13.5=n. Theexposing conditions are NA=0.25 and σ=0.70.

To produce the above exposure mask 10, it is necessary to properlydecide a film thickness of the TaN film 14. The present inventionfeatures a process for deciding the film thickness of the TaN film 14.

The decision process will be described in brief. FIG. 2 is a flow chartshowing an example of the film thickness decision process according tothe present invention. As shown in the figure, when a forming filmthickness of the absorber film 14 is decided, the swing effect and thebulk effect that occur on a transferred image of a pattern formed withthe TaN film 14 are specified (at step 101, hereinafter step isabbreviated as “S”). In this example, the swing effect and the bulkeffect that occur against a line width of the transferred image (patternwidth) are specified. The swing effect and bulk effect occur due to theinfluence of the TaN film 14 and the Ru film 13. Thus, the swing effectand the bulk effect can be specified by, for example, a logicalcalculation, a simulation, or the like in accordance with thecharacteristic values of the forming materials of the TaN film 14 andthe Ru film 13 and exposure optical conditions.

After the swing effect and the bulk effect that occur against a linewidth are specified, the OD as the decision condition of the formingfilm thickness of the TaN film 14 is decided in consideration of thespecified swing effect and bulk effect so that the line width variationis at its minimum (at S102). Thus, the forming film thickness of the TaNfilm 14 can be estimated. In other words, the reference of the formingfilm thickness of the TaN film 14 is decided.

However, this does not mean that the film thickness of the TaN film 14can be freely specified in accordance with the decided OD. After the ODhas been decided, the swing effect and the bulk effect are specified (atS103). In particular, the swing effect and the bulk effect against apattern shift of a transferred image are specified. They are specifiedin the same manner as those against a line width. On the other hand, thefilm forming accuracy of the TaN film 14 that depends on the performanceof a film forming apparatus forming the TaN film 14 is obtained (atS104). Thus, the fluctuation of the forming film thickness of the TaNfilm 14 can be estimated.

Thereafter, the forming film thickness of the TaN film 14 is decided inconsideration of the specified swing effect and bulk effect and the filmforming accuracy of the TaN film 14 so that the pattern shift is at itsminimum (at S105). Thus, the forming film thickness of the TaN film 14in which the line width variation and the pattern shift are at theirminimum is decided.

Next, a concrete example of the forgoing decision process will bedescribed. First of all, specifying the swing effect and bulk effect dueto multiple interferences in the TaN film 14 and the Ru film 13 will bedescribed (at S101 in FIG. 2). As described above, the swing effect andbulk effect are specified by, for example, a theoretical calculation,simulation, or the like in accordance with the characteristic values ofthe forming materials of the TaN film 14 and Ru film 13 and the exposureoptical conditions. Since these methods can be performed by knowntechniques, their description will be omitted.

FIG. 3 to FIG. 6 are schematic diagrams describing concrete examples ofspecified results of the swing effect and the bulk effect. In theseexamples, assuming that the film thickness of the Ru film 13 is 30 nm,the swing effect and the bulk effect are specified. FIG. 3 shows theswing effect and the bulk effect with plotted values against a linewidth for a film thickness of the TaN film 14 in the case that a patternhaving a width of 40 nm is formed on a mask (on a wafer: 160 nm on a −4×mask). The pattern pitch is 160 nm and the incident angle against thenormal line of the mask surface is 4.84 degrees. In the drawing, anapproximated curve line against the line width represents the bulkeffect against the line width. FIG. 4 shows the swing effect and thebulk effect with plotted values against a pattern shift for a filmthickness of the TaN film 14 in the case that a pattern having a widthof 40 nm is formed on a mask (on a wafer: 160 nm on a 4× mask). In thedrawing, an approximate straight line against the pattern shiftrepresents the bulk effect against the pattern shift. FIG. 5 shows onlythe swing effect with plotted values against a line width for a filmthickness of the TaN film 14 in the case that a pattern having a widthof 40 nm is formed on a mask (on a wafer: 160 nm on a −4× mask) withOD=around 3. FIG. 6 shows only the swing effect with plotted valuesagainst the pattern shift for a film thickness of the TaN film 14 in thecase that a pattern having a width of 40 nm is formed on a mask (on awafer: 160 nm on a −4× mask) with OD=around 3.

As is clear from FIG. 3 to FIG. 6, the swing effect and bulk effect,that are the specified result, vary as the film thickness of the TaNfilm 14 increases as follows. In other words, the swing effect against aline width gradually decreases as the film thickness of the TaN film 14increases (see FIG. 3 and FIG. 5). In contrast, the swing effect againstthe pattern shift gradually increases as the film thickness of the TaNfilm 14 increases (see FIG. 4 and FIG. 6). In addition, the bulk effectagainst a line width decreases, as the film thickness of the TaN film 14increases, by a quadratic curve so as to be preferably approached (seeFIG. 3). In contrast, the bulk effect against the pattern shift isconstant regardless of the film thickness of the TaN film 14 so as to bepreferably approached by a linear curve (see FIG. 4).

Next, the OD that is decided in accordance with the specified swingeffect and bulk effect will be described (S102 shown in FIG. 2). The ODis decided in accordance with the swing effect and bulk effect against aline width (see FIG. 3 and FIG. 5). The OD is a deciding condition ofthe forming film thickness of the TaN film 14. The OD has a relationwith the film thickness of the TaN film 14 as shown in FIG. 7. FIG. 7 isa schematic diagram describing a concrete example of the relation of theOD and the film thickness of the TaN film 14.

As described above, conventionally, the value of the OD was decided withonly the reflectance on the surface of the TaN film 14 (absorber film)without consideration of the swing effect and bulk effect. Thus, it wasthought that even if OD=2, a good pattern can be formed. FIG. 7 showsthat with OD=3 the film thickness of the TaN film 14 is around 120 nm,and with OD=2 the film thickness of the TaN film 14 is around 80 nm.However, when the forming film thickness of the TaN film 14 fluctuatesdue to the influence of the film forming accuracy, as is clear from therelation between the fluctuation of the film thickness and the linewidth variation, the range of the line width variation of thetransferred line with OD=2 is larger than that with OD=3.

Thus, the OD is decided in consideration of the swing effect and bulkeffect against a line width (see FIG. 3 and FIG. 5) so that the linewidth variation is at its minimum. More specifically, it is found thatthe range of the line width variation of the transferred line with OD=3is preferably smaller than that with OD=2. Thus, it is decided that, forexample, OD=3. The forming film thickness of the TaN film 14 is decidedwith a reference of OD=3.

The film thickness of the TaN film 14 can be decided in accordance withonly the OD decided as above (see FIG. 3). However, since the filmthicknesses of the TaN film 14 and the Ru film 13 fluctuate inpredetermined ranges due to the influence of the film forming accuraciesthereof, it is not mean that the film thickness of the TaN film 14 canbe freely specified in accordance with the decided OD. Instead, it isthought that an optimum portion exists for a good transferred image.

FIG. 8 is a schematic diagram describing the swing effect and the bulkeffect with plotted values against a line width in the case that apattern having a width of 40 n is formed on a mask (on a wafer: 160 nmon a 4× mask) and that the film thickness of the TaN film 14 is fixedand the film thickness of the Ru film 13 is varied with the OD of around3. FIG. 9 is a schematic diagram describing the swing effect and thebulk effect with plotted values against a pattern shift in the case thata pattern having a width of 40 nm is formed on a mask (on a wafer: 160nm on a 4× mask) and that the film thickness of the TaN film 14 is fixedand the film thickness of the Ru film 13 is varied with the OD of around3. It is found from these drawings that the swing effect against a linewidth, the swing effect against pattern shift, the bulk effect against aline width, and the bulk effect against pattern shift occur when thefilm thickness of the Ru film 13 is varied like those when the filmthickness of the TaN film 14 is varied.

FIG. 10 is a schematic diagram describing the swing effect and the bulkeffect with plotted values against a line width in the case that apattern having a width of 40 nm is formed on a mask (on a wafer: 160 nmon a 4× mask) and that film thicknesses of the TaN film 14 and the Rufilm 13 are varied. FIG. 11 is a schematic diagram describing the swingeffect and the bulk effect with plotted values against a pattern shiftin the case that a pattern having a width of 40 nm is formed on a mask(on a wafer: 160 nm on a 4× mask) and that the film thicknesses of boththe TaN film 14 and the Ru film 13 are varied. It is found from FIG. 10that when the forming fluctuation of the film thickness of the TaN film14 is, for example, ±3 nm and the forming fluctuation of the filmthickness of the Ru film 13 is, for example, ±3 nm, the line widthvariation due to the influence of these fluctuations of the filmthickness is around 1.4 nm On the other hand, FIG. 11 shows that sincethe influence of the bulk effect due to the film thicknesses of the TaNfilm 14 and the Ru film 13 is large, the pattern shift has a node whenthe film thickness of the TaN film 14 is around 123 nm and has a loopwhen it is not 123 nm.

Since there are a node and a loop, it can be said that there is anoptimum portion of the film thickness of the TaN film 14 for obtaining agood transferred image when the forming film thicknesses of the TaN film14 and the Ru film 13 fluctuate. Thus, after the OD has been decided, aprocess for obtaining the optimum portion of the TaN film 14 isperformed in consideration of the fluctuation of the film thickness ofthe Ru film 13 (at S103 to S105 shown in FIG. 2).

To obtain the optimum portion of the film thickness, the swing effectand the bulk effect are specified (at S103 shown in FIG. 2). The methodfor specifying the swing effect and the bulk effect is the same as theforegoing method (at S101 shown in FIG. 2).

FIG. 12 to FIG. 15 are schematic diagrams describing another concreteexample of specified results of the swing effect and the bulk effect.FIG. 12 shows the swing effect and the bulk effect with plotted valuesagainst a line width in the case that a pattern having a width of 30 nmis formed on a mask (on a wafer: 120 nm on a 4× mask) and that the filmthicknesses of the TaN film 14 and the Ru film 13 are varied at anincident angle of 4.84 degrees. FIG. 13 shows the swing effect and thebulk effect with plotted values against a pattern shift in the sameconditions. FIG. 14 shows the swing effect and the bulk effect withplotted values against a line width in the case that a pattern having awidth of 30 μm is formed on a mask (on a wafer: 120 nm on a 4× mask) andthat the film thicknesses of the TaN film 14 and the Ru film 13 arevaried at an incident angle of 7.27 degrees. FIG. 15 shows the swingeffect and the bulk effect with plotted values against a pattern shiftin the same conditions. The pattern pitch is 160 nm (on a wafer: 640 nmon a 4× mask).

Thereafter, a process for deciding the optimum value of the filmthickness of the TaN film 14 in consideration of the specified swingeffect and bulk effect will be described (at S105 shown in FIG. 2). Itis assumed that before the optimum value is decided, the fluctuations ofthe forming film thicknesses of the TaN film 14 and the Ru film 13,namely the film forming accuracies of the films 13 and 14, have beenobtained (at S104 shown in FIG. 2). The film forming accuracies areobtained in accordance with the performance of a film forming apparatusthat forms the films 13 and 14, film forming conditions, and so forth.In the following description, it is assumed that the film formingaccuracies are in the range of ±0 nm to ±3 nm.

It is assumed that the incident angle is 4.84 degrees. Assuming that thefilm thickness of the TaN film 14 is ±0 nm, it is found from FIG. 12that the film thickness of the TaN film 14 in which the line widthvariation is at its minimum is 126 nm. At that point, the range of theline width variation is 1.64 nm. In addition, it is found from FIG. 13that the film thickness of the TaN film 14 in which the pattern shift ofthe pattern is at its minimum is 123 nm. At that point, the range of thefluctuation of the pattern shift is 0.24 nm.

Assuming that the fluctuation of the film thickness of the TaN film 14is ±1 nm, it is found from FIG. 12 that the film thickness of the TaNfilm 14 in which the line width variation is at its minimum is 126 nm.At that point, the range of the line width variation is 1.64 nm. Inaddition, it is found from FIG. 13 that the film thickness of the TaNfilm 14 in which the pattern shift is at its minimum is 123 nm. At thatpoint, the range of the fluctuation of the pattern shift is 0.34 nm.

In addition, assuming that the fluctuation of the film thickness of theTaN film 14 is ±2 nm, it is found from FIG. 12 that the film thicknessof the TaN film 14 in which the line width variation is at its minimumis 125 nm. At that point, the range of the line width variation is 1.86nm. In addition, it is found from FIG. 13 that the film thickness of theTaN film 14 in which the pattern shift is at its minimum is 121 nm. Atthat point, the range of the fluctuation of the pattern shift is 0.39nm.

In addition, assuming that the fluctuation of the film thickness of theTaN film 14 is ±3 nm, it is found from FIG. 12 that the film thicknessof the TaN film 14 in which the line width variation is at its minimumis 123 nm. At that point, the range of the line width variation is 1.89nm. In addition, it is found from FIG. 13 that the film thickness of theTaN film 14 in which the pattern shift is at its minimum is 120 nm. Atthat point, the range of the fluctuation of the pattern shift is 0.39nm.

On the other hand, assuming that the fluctuation of the film thicknessof the TaN film 14 is ±3 nm, it is found that from FIG. 12 that the filmthickness of the TaN film 14 in which the line width variation is at itsminimum is 120 nm. At that point, the range of the line width variationis 1.92 nm. In addition, it is found from FIG. 13 that the filmthickness of the TaN film 14 in which the pattern shift is at itsminimum is 123 nm. At that point, the range of the fluctuation of thepattern shift is 0.55 nm.

As described above, the film thickness of the TaN film 14 does notrepresent the relation in which when the line width variation is at itsminimum, the fluctuation of the pattern shift is at its minimum.Instead, the film thickness of the TaN film 14 represents the relationof a trade-off between the line width variation and the fluctuation ofthe pattern shift. However, even in the relation of the trade-off, therange of the fluctuation of the pattern shift is smaller than the rangeof the line width variation.

Thus, when the optimum value of the film thickness of the TaN film 14 isdecided by extracting the film thickness in which the range of thefluctuation of the pattern shift, namely, the pattern shift is at itsminimum, the extracted film thickness is decided as the optimum value.For example, when the fluctuation of the film thickness of the TaN film14 is ±3 nm, 120 nm is chosen as the optimum value of the film thicknessof the TaN film 14. When the fluctuation of the film thickness of theTaN film 14 is ±2 nm, 121 nm is chosen as the optimum value of the filmthickness of the TaN film 14. When the fluctuation of the film thicknessof the TaN film 14 is ±1 nm, 123 nm is chosen as the optimum value ofthe film thickness of the TaN film 14.

This process applies also to the case that the incident angle is 7.27degrees. For example, assuming that the fluctuation of the filmthickness of the TaN film 14 is ±0 nm, it is found from FIG. 14 that thefilm thickness of the TaN film 14 in which the pattern shift is at itsminimum is 120 nm. At that point, the range of the line width variationis 1.64 nm. In addition, it is found from FIG. 15 that the filmthickness of the TaN film 14 in which the pattern shift is at itsminimum is 123 nm. At that point, the range of the fluctuation of thepattern shift is 0.35 nm.

In addition, assuming that the fluctuation of the film thickness of theTaN film 14 is ±1 nm it is found from FIG. 14 that the film thickness ofthe TaN film 14 in which the line width variation is at its minimum is120 nm. At that point, the range of the line width variation is 1.78 nm.In addition, it is found from FIG. 15 that the film thickness of the TaNfilm 14 in which the pattern shift is at its minimum is 123 nm. At thatpoint, the range of the fluctuation of the pattern shift is 0.56 nm.

In addition, assuming that the fluctuation of the film thickness of theTaN film 14 is ±2 nm, it is found from FIG. 14 that the film thicknessof the TaN film 14 in which the line width variation is at its minimumis 122 nm. At that point, the range of the line width variation is 2.00.In addition, it is found from FIG. 15 that the film thickness of the TaNfilm 14 in which the pattern shift is at its minimum is 121 nm. At thatpoint, the range of the fluctuation of the pattern shift is 0.57 nm.

In addition, assuming that the fluctuation of the film thickness of theTaN film 14 is ±3 nm, it is found from FIG. 14 that the film thicknessof the TaN film 14 in which the line width variation is at its minimumis 123 nm. At that point, the range of the line width variation is 2.03nm. In addition, it is found from FIG. 15 that the film thickness of theTaN film 14 in which the pattern shift is at its minimum is 120 nm. Atthat point, the range of the fluctuation of the pattern shift is 0.58nm.

On the other hand, assuming that the fluctuation of the film thicknessof the TaN film 14 is ±3 nm, it is found from FIG. 14 that the filmthickness of the TaN film 14 in which the line width variation is at itsmaximum is 120 nm. At that point, the range of the line width variationis 2.33 nm. In addition, it is found from FIG. 15 that the filmthickness of the TaN film 14 in which the pattern shift is at itsmaximum is 124 nm. At that point, the range of the fluctuation of thepattern shift is 0.83 nm.

Thus, in the case that the incident angle is 7.27 degrees, the filmthickness of the TaN film 14 represents the relation of trade-offbetween the line width variation and the fluctuation of the patternshift. The range of the line width variation is smaller than that of thepattern shift. Thus, in this case, the film thickness in which thepattern shift is at its minimum is decided as the optimum value of thefilm thickness of the TaN film 14. For example, assuming that thefluctuation of the film thickness of the TaN film 14 is ±3 nm, 120 nm ischosen as the optimum value of the film thickness of the TaN film 14 inwhich the range of the fluctuation of the pattern shift is at itsminimum. In addition, assuming that the fluctuation of the filmthickness of the TaN film 14 is ±2 nm, 121 nm is chosen as the optimumvalue of the film thickness of the TaN film 14. When the fluctuation ofthe film thickness of the TaN film 14 is ±1 nm, 123 nm is chosen as theoptimum value of the film thickness of the TaN film 14.

In the foregoing decision process, the film thickness of the TaN film 14is decided. The exposure mask 10 on which the TaN film 14 has beenformed in accordance with the decision result is used. In this case,even if the swing effect and the bulk effect occur on a transferredimage on a wafer or even if the forming film thicknesses of the TaN film14 and the Ru film 13 fluctuate, the line width variation of thetransferred image and the pattern shift can be minimized. Thus, thereflection type exposure mask 10 for extreme ultraviolet light iscapable of properly dealing with a miniaturized structure of a patternwidth, a pattern pitch, and so forth of a transferred image. As aresult, the present embodiment is capable of contributing to theimprovement of a semiconductor device.

According to the present embodiment, it is described that when the filmthickness of the TaN film 14 is decided, the OD is decided so that theline width variation is at its minimum and further the optimum value ofthe film thickness of the TaN film 14 is decided in accordance with thedecided OD so that the pattern shift is at its minimum. However, itshould be noted that the present invention is not limited to theforegoing example. In other words, the process of deciding both the ODand the optimum value of film thickness of the TaN film 14 is mostsuitably performed by the above-recited exemplary method. However, byemploying another method (of a conventional technology or the like),with one of the OD and the optimum value of the film thickness, the filmthickness of the TaN film 14 can be decided. In this case, inconsideration of the swing effect and the bulk effect, the line widthvariation and the pattern shift of the transferred image can be moresuppressed than before.

In addition, according to the present embodiment, it is described thatwhen the film thickness of the TaN film 14 is decided, the OD is decidedin accordance with the line width so that the line width variation is atits minimum, while, on the other hand, the optimum value of the filmthickness is decided in accordance with the pattern shift so that thepattern shift is at its minimum. However, it should be noted that thepresent invention is not limited to the foregoing examples. For example,the OD may be decided in accordance with the pattern shift or theoptimum value of the film thickness may be decided in accordance withthe line width. Alternatively, the OD and the optimum value of the filmthickness may be decided in accordance with both the line width and thepattern shift. In other words, the OD and the optimum value of the filmthickness may be decided with either or both of the line width variationof the transferred image and the amount of the pattern shift, whichbecome clear from the specified results of the swing effect and the bulkeffect. In addition, according to the present embodiment, an example inwhich the TaN film 14 functions as an absorber film and the Ru film 13functions as a buffer film is described. However, it should be notedthat the forming material of each film is not limited to the foregoingexample.

Next, a method for producing a semiconductor device using the exposuremask 10 described above will be described. FIG. 16 is a flow chartshowing an example of a process of a method for producing asemiconductor device, the process including a step for using an exposuremask to which the present invention is applied. In the drawing, step(S101), which specifies the swing effect and the bulk effect that mayoccur on a transferred image of a pattern formed with the TaN film 14 ofthe exposure mask 10, to step (S105), which decides a forming filmthickness of the TaN film 14, are similar to those of the foregoingexample (see FIG. 2). Thus, their description will be omitted.

After the forming film thickness of the TaN film 14 has been decided,the exposure mask 10 having the structure shown in FIG. 1 is produced inaccordance with the decision results (at S106). As a result, theexposure mask 10 on which the TaN film 14 has been formed for the filmthickness in which the line width variation and the pattern shift are attheir minimum values is obtained. Since the films 13 and 14 are formedby a known technology, their description will be omitted.

Thereafter, with the produced exposure mask 10, a wafer as an exposureobject is exposed with a beam (exposure light) having the samewavelength as light reflected by the mask blanks 12 of the exposure mask10 (at S107). In other words, a lithography process for forming acircuit pattern of a semiconductor device is performed with the exposuremask 10.

Thus, since the exposure mask 10 has the TaN film 14 having a filmthickness that allows the line width variation and the pattern shiftexposed on a wafer to be at their minimum, the exposure mask 10 iscapable of properly miniaturizing the pattern width, pattern pitch, andso forth of a transferred image. In other words, when a semiconductordevice is produced by a process including a lithography process usingthe exposure mask 10, since the line width variation and the patternshift exposed on a wafer are at their minimum, the exposure mask 10 iscapable of contributing to the improvement of a semiconductor device (asa proper approach for miniaturization of a semiconductor device).

As a beam for exposing an object, X-ray, radiation beam, radiation ray,charged particle radiation, ultraviolet ray, ultraviolet light, visiblelight, or a ray of light can be used, as well as extreme ultravioletlight, for the present invention.

As an example of an electron beam exposing technology, the low energyelectron proximity projection lithography (LEEPL) is known. In theLEEPL, a stencil mask of which holes corresponding to a device patternare formed in a membrane having a thickness of several 100 nm is used. Amask is placed immediately above a wafer so that the space therebetweenbecomes around several 10 μm By scanning a pattern portion of the maskwith an electron beam of several 10 keV, the pattern is transferred tothe wafer (T. Utsumi, Journal of Vacuum Science and Technology B 17,2897 (1999)). Thus, an electron beam that is emitted from a lowacceleration electron gun passes through an aperture. A condenser lenscauses the electron beam to become a parallel beam. The parallel beampasses through a deflector and irradiates a wafer through a mask In thiscase, when the exposure mask according to the present invention is used,the pattern width, pattern pitch, and so forth of a transferred imagecan be properly miniaturized. As a result, the exposure mask accordingto the present invention is capable of contributing to the improvementof the performance of the semiconductor device.

In addition, a method of which a small-segmented membrane is supportedby a grid structure is known. The method is used for a mask in SCALPEL(scattering with angular limitation in projection electron-beamlithography), PREVAIL (projection exposure with variable axis immersionlenses), and an EB stepper (for example, L. R. Harriott, Journal ofVacuum Science and Technology B15, 2130 (1997); H. C. Pfeiffer, JapaneseJournal of Applied Physics 34,6658 (1995)). In SCALPEL, an electron beamthat is emitted from a low acceleration electron beam passes through anaperture. A condenser lens causes the electron beam to become a parallelbeam. The parallel beam irradiates a wafer through a deflector and amask In PREVAIL, a condenser lens, a reticule, a first projection lens,a crossover aperture, a second projection lens, a sample, and anunder-sample lens are disposed in that order from the electron beamsource side. In the structure, a reticule pattern is transferred in areduced size to the sample. In these cases, with the exposure maskaccording to the present invention, the pattern width, pattern pitch,and so forth of a transferred image can also be properly miniaturized.As a result, the exposure mask according to the present invention cancontribute to the improvement of the performance of the semiconductordevice.

INDUSTRIAL APPLICABILITY

Since the forming film thickness of the absorber film is decided inconsideration of the swing effect and the bulk effect due to theinfluence of the absorber film and the buffer film, the line widthvariation and the pattern shift exposed on the wafer are at theirminimum values, even for a reflection type exposure mask for extremeultraviolet light. Thus, the exposure mask allows the pattern width, thepattern pitch, and so forth of a transferred image to be miniaturized.As a result, the exposure mask is capable of contributing to theimprovement of the performance of the semiconductor device.

1. A method for producing a reflective exposure mask, the reflectiveexposure mask including: a stack of reflective layers for reflectingexposure light; an absorber film functioning to absorb said exposurelight for covering a light reflection plane side of said stack ofreflective layers with a predetermined pattern; and a buffer filminterposed between said stack of reflective layers and said absorberfilm; said method comprising the steps of: specifying a swing effect anda bulk effect, which occur on a transferred image on said exposureobject due to multiple reflections within said absorber film and saidbuffer film to at least one fluctuation of a line width and patternshift in a transferred portion of said predetermined pattern, inaccordance with characteristic values of forming materials of saidabsorber film and said buffer film and optical conditions when exposing,upon deciding a forming film thickness of said absorber film; anddeciding an optical density that is a deciding condition of said formingfilm thickness of said absorber film in consideration of said specifiedswing effect and said specified bulk effect so that said fluctuation ofsaid line width of said pattern and/or pattern shift of said pattern isminimized.
 2. The method for producing the reflective exposure maskaccording to claim 1, wherein said exposure light is extreme ultravioletlight, X-ray, radiation ray, ultraviolet light, or visible light.
 3. Themethod for producing the reflective exposure mask according to claim 1,wherein said absorber film is a film made of tantalum nitride.
 4. Themethod for producing the reflective exposure mask according to claim 1,wherein said buffer film is a film made of ruthenium.
 5. The method forproducing the reflective exposure mask according to claim 1, whereinsaid absorber film is a film made of tantalum nitride and said bufferfilm is a film made of ruthenium.
 6. A method for producing a reflectiveexposure mask, the reflective exposure mask including: a stack ofreflective layers for reflecting exposure light; an absorber filmfunctioning to absorb said exposure light for covering a lightreflection plane side of said stack of reflective layers with apredetermined pattern; and a buffer film interposed between said stackof reflective layers and said absorber film; said method comprising thesteps of: specifying a swing effect and a bulk effect, which occur on atransferred image on said exposure object due to multiple reflectionswithin said absorber film and said buffer film to at least onefluctuation of a line width and pattern shift in a transferred portionof said predetermined pattern, in accordance with characteristic valuesof forming materials of said absorber film and said buffer film andoptical conditions when exposing, upon deciding a forming film thicknessof said absorber film; and deciding an optical density that is adeciding condition of said forming film thickness of said absorber filmin consideration of said specified swing effect, said specified bulkeffect and forming accuracy when said absorber film is formed so thatsaid fluctuation of said line width of said pattern and/or pattern shiftof said pattern is minimized.
 7. The method for producing the reflectiveexposure mask according to claim 6, wherein said exposure light isextreme ultraviolet light, X-ray, radiation ray, ultraviolet light, orvisible light.
 8. The method for producing the reflective exposure maskaccording to claim 6, wherein said absorber film is a film made oftantalum nitride.
 9. The method for producing the reflective exposuremask according to claim 6, wherein said buffer film is a film made ofruthenium.
 10. The method for producing the reflective exposure maskaccording to claim 6, wherein said absorber film is a film made oftantalum nitride and said buffer film is a film made of ruthenium.
 11. Areflective exposure mask used for exposing an exposure object in aproduction process of a semiconductor device, the reflective exposuremask comprising: a stack of reflective layers for reflecting exposurelight; an absorber film functioning to absorb said exposure light forcovering a light reflection plane side of said stack of reflectivelayers with a predetermined pattern; and a buffer film interposedbetween said stack of reflective layers and said absorber film; whereina swing effect and a bulk effect, which occur on a transferred image onsaid exposure object due to multiple reflections within said absorberfilm and said buffer film to at least one fluctuation of a line widthand pattern shift in a transferred portion of said predeterminedpattern, is specified in accordance with characteristic values offorming materials of said absorber film and said buffer film and opticalconditions when exposing, upon deciding a forming film thickness of saidabsorber film; and an optical density that is a deciding condition ofsaid forming film thickness of said absorber film is decided inconsideration of said specified swing effect and said specified bulkeffect so that said fluctuation of said line width of said patternand/or pattern shift of said pattern is minimized.
 12. The reflectiveexposure mask according to claim 11, wherein said exposure light isextreme ultraviolet light, X-ray, radiation ray, ultraviolet light, orvisible light.
 13. A reflective exposure mask used for exposing anexposure object in a production process of a semiconductor device,comprising: a stack of reflective layers for reflecting exposure light,an absorber film functioning to absorb said exposure light for coveringa light reflection plane side of said stack of reflective layers with apredetermined pattern, and a buffer film interposed between said stackof reflective layers and said absorber film; wherein a swing effect anda bulk effect, which occur on a transferred image on said exposureobject due to multiple reflections within said absorber film and saidbuffer film to at least one fluctuation of a line width and patternshift in a transferred portion of said predetermined pattern, isspecified in accordance with characteristic values of forming materialsof said absorber film and said buffer film and optical conditions whenexposing, upon deciding a forming film thickness of said absorber film;and an optical density that is a deciding condition of said forming filmthickness of said absorber film is decided in consideration of saidspecified swing effect, said specified bulk effect and forming accuracywhen said absorber film is formed so that said fluctuation of said linewidth of said pattern and/or pattern shift of said pattern is minimized.14. The reflective exposure mask according to claim 13, wherein saidexposure light is extreme ultraviolet light, X-ray, radiation ray,ultraviolet light, or visible light.
 15. A method of using a reflectiveexposure mask for producing a semiconductor device, the reflectiveexposure mask including: a stack of reflective layers for reflectingexposure light; an absorber film functioning to absorb said exposurelight for covering a light reflection plane side of said stack ofreflective layers with a predetermined pattern; and a buffer filminterposed between said stack of reflective layers and said absorberfilm; said method comprising the steps of: specifying a swing effect anda bulk effect, which occur on a transferred image on said exposureobject due to multiple reflections within said absorber film and saidbuffer film to at least one fluctuation of a line width and patternshift in a transferred portion of said predetermined pattern, inaccordance with characteristic values of forming materials of saidabsorber film and said buffer film and optical conditions when exposing,upon deciding a forming film thickness of said absorber film; anddeciding an optical density that is a deciding condition of said formingfilm thickness of said absorber film in consideration of said specifiedswing effect and said specified bulk effect so that said fluctuation ofsaid line width of said pattern and/or pattern shift of said pattern isminimized.
 16. The method according to claim 15, wherein said exposurelight is extreme ultraviolet light, X-ray, radiation ray, ultravioletlight, or visible light.
 17. The method according to claim 15, whereinsaid absorber film is a film made of tantalum nitride and said bufferfilm is a film made of ruthenium.
 18. A method for producing asemiconductor device by using a reflective exposure mask, the reflectiveexposure mask including: a stack of reflective layers for reflectingexposure light, an absorber film functioning to absorb said exposurelight for covering a light reflection plane side of said stack ofreflective layers with a predetermined pattern, and a buffer filminterposed between said stack of reflective layers and said absorberfilm; said method comprising the steps of: specifying a swing effect anda bulk effect, which occur on a transferred image on said exposureobject due to multiple reflections within said absorber film and saidbuffer film to at least one fluctuation of a line width and patternshift in a transferred portion of a predetermined pattern, in accordancewith characteristic values of forming materials of said absorber filmand said buffer film and optical conditions when exposing, upon decidinga forming film thickness of said absorber film; and deciding an opticaldensity that is a deciding condition of said forming film thickness ofsaid absorber film in consideration of said specified swing effect, saidspecified bulk effect and forming accuracy when said absorber film isformed so that said fluctuation of said line width of said patternand/or pattern shift of said pattern is minimized.
 19. The method forproducing a semiconductor device according to claim 18, wherein saidexposure light is extreme ultraviolet light, X-ray, radiation ray,ultraviolet light, or visible light.
 20. The method for producing asemiconductor device according to claim 18, wherein said absorber filmis a film made of tantalum nitride and said buffer film is a film madeof ruthenium.